Fuel rod fabrication

ABSTRACT

A process of sealing the external junction between an endclosure and a long fuel rod of a slender nature in a controlled gaseous environment by a rotating electrode passing through a predetermined path around the periphery of the junction. A device for accomplishing the aforesaid process wherein the fuel rod is held in a horizontal attitude at a predetermined position while a rotating electrode operatively fuses the endclosure to such fuel rod.

Elnite Sites atent [19] 81114 et a1.

[451 Aug. 13, 19741 FUEL ROD FABRICATION [75] Inventors: Edmond J. Silk, Lynchburg; Claude A. Moore, Appomattox, both of Va.

[73] Assignee: The Babcock & Wilcox Company,

[58] Field of Search 53/88, 37, 83, 112 R, 334, 53/7, 9, 367, 22 R, 12; 29/400 N; 228/29, 32; 219/137, 221 P; 176/67, 87, 76

[56] References Cited UNITED STATES PATENTS 1,790,787 2/1931 Badger 53/83 2,481,042 9/1949 Tomasek et a1. 53/83 X 2,816,407 12/1957 Brockmann 53/37 2,884,748 5/1959 Berg 53/37 X 2,893,182 7/1959 Pies 53/37 X 2,994,169 8/1961 Fliezar et al.. 53/112 R 3,256,672 6/1966 Palmer 53/88 3,389,846 6/1968 Claffey 228/29 3,725,635 4/1973 Fink et al 176/79 X Primary Examiner-Travis S. McGehee Assistant Examiner-Horace M. Culver Attorney, Agent, or Firm-J. M. Maguire; J. P. Sinnott [5 7] ABSTRACT A process of sealing the external junction between an end-closure and a long fuel rod of a slender nature in a controlled gaseous environment by a rotating electrode passing through a predetermined path around the periphery of the junction.

A device for accomplishing the aforesaid process wherein the fuel rod is held in a horizontal attitude at a predetermined position while a rotating electrode operatively fuses the end-closure to such fuel rod.

2 Claims, 3 Drawing Figures MENU-ID AUB I 31974 SHEE? 2 [IF FUEL ROD FABRICATION This invention relates to the fabrication of fuel rods of the nuclear variety.

More particularly, this invention relates to a process of sealing end closures-to fuel rods containing radioactive fuel in an inert gaseous environment under pressure and a device for accomplishing the same.

In the process of fabricating fuel rods of a nuclear nature, closures must be sealed in position on the end of relatively long slender rods containing radioactive fuel maintained in an inert gaseous medium under pressure. The classical method of sealing such end-closures to fuel rods incorporated large and complicated evacuation chambers with excessive pump-down time inherently resulting in low production capabilities, high capital cost and very large spacial requirements for set-up of the sealing apparatus.

What is needed in the art is a process of sealing the external juncture or joint between the end-closure and fuel rod in a horizontal position, since welding the twelve-foot lengths of tubing in a vertical position would require high interior working platform or, in the alternative, relative deep pits. It should also be necessary to rotate the sealing means, rather than the twelvefoot tube, to eliminate the necessity for rotating supports and possible damage of the radioactive material. Also, the actual enclosure used for sealing should be as small as practical to decrease the pumpdown time, the consumption of inert gas and to minimize the total time expended in processing. The latter should also be facilitated by having only a short length of the slender rods actually intrude the chamber. The total process time from insertion of the fuel rod into the enclosure through evacuation and sealing in the desired environment to cooling should not exceed a fraction .of the time required by conventional techniques.

The subject invention answers the needs of the art with special emphasis on the achievement of a totally effective processing technique having optimum efficiency in the shortest possible time without encountering the aforesaid difficulties of the art.

It is therefore an object of this invention to provide an improved process of sealing an end-closure to a relatively long nuclear fuel rod of a slender nature and a device for accomplishing the same.

Other objects and many of the attendant advantages of this invention will be more readily understood from a reading of the following detailed description when taken with the accompanying drawings wherein:

FIG. 1 is a top plan view in section of the device of this invention.

FIG. 2 is a side view in section of the device of FIG. 1.

FIG. 3 is a front view in section of the same device.

Similar numerals refer to similar parts throughout the several views.

The subject invention encompasses the longitudinal insertion of a linear workpiece of the nuclear fuel rod variety having an end-closure to a predetermined position into an enclosure having a controlled inert gaseous environment under pressure, then securing such workpiece in position relative to the peripheral circuit of a sealing means of a welding nature, subsequently sealing the external junction formed between such closure and such fuel rod, and extracting such fuel rod in sealed condition ready for use in the core of a nuclear reactor.

In the preferred embodiment as shown in FIGS. l3, the device for use in the present process is provided with an enclosure or chamber 10 having means for control of environment therein. The latter means is in the form of an aperture 11 in the lower surface of the chamber which operatively communicates in controlled alternate fashion with either an evacuation pump 12 or a gaseous environmental source 13 maintained under pressure. The ends of the chamber are each provided with a port which are in axial alignment with each other. The ports 14 and 15 are each provided with sealing means 16 and 17 of the conventional variety for use in maintaining the desired environment within the chamber. The entrance port 14 is adapted for receptive insertion of one end of the fuel rod 18 while the exit port 15 is adapted to insure external travel of such fuel rod 18 through a sealed communicating circuit of piping into an external glove box (not shown) after traversement of the chamber as will be hereinafter more clearly described.

The chamber 10 is provided with insulated base means 21 having a supporting housing 22 within which is rotatably mounted a cylindrical shaft 23 having a longitudinal passageway 24 of open end construction in axial alignment with the aforesaid ports 14 and 15.

Referring now toFIGS. 1 and 2, a cylindrical support plate 25 is operatively mounted in one end of the shaft and is provided with an opening26 in axial alighment with the passageway 24 of the shaft 23. A sealing device 27 of the TIG welding variety is supportably mounted on the outer peripheral portion of the plate 25, as shown in FIG. 2, and is positioned so that the head 28 thereof travels in a predetermined course around the periphery of the fuel rod 18 when the shaft 23 with its attached plate 25 is revolved within the housing 22.

Referring now to FIG. 1. electrical contact fingers 31 provides power to operate the welding device 27 from a power source (not shown) while movement of the plate 25 around its axis is imparted through the gear train 32 and 33 from a motive source 34. In this way, the operating welding head 27 is rotated in an annular path around the periphery of the fuel rod 18.

As shown in FIG. 1, a cylindrical cam 36 of the buttonvariety is mounted on the support housing 22 for separable engagement with the body of the welding device 27 through an arm 37 during the processing of a plurality of fuel rods 18. The cam 36 is operatively connected to a double action air cylinder 39, which is electrically controlled by a power source (not shown) through the use of conventional circuitry, for the extension of such cam 36 upon completion of the welding cycle and the retraction of such cam 36 upon the initiation of a new cycle. This eliminates the possibility of the fuel rod 18 striking and damaging the electrode or head 28 during insertion or removal of the fuel rod from the chamber 10.

An arm 41 is pivotally mounted on the base 21 by means of a' shaft 42 through a support 43 and is designed, when actuated, to travel to a position intersecting the axial path of the fuel rod 18 as shown in FIG. 2. In this way, the retractable arm 41 functions in the form of a stop against further linear movement of the fuel rod 18 and the latter is in a predetermined position for the operative sealing of the external juncture between the end-closure and fuel rod by the electrode or head 28. As shown in FlG. 1-3, the arm 41 is actuated into pivotal motion by an air cylinder 44 of the pushpull variety through a linkage 45 which communicates with the shaft 42. The two step air cylinder 44 is such that it functions to extend and retract the linkage 45 by the action of the power source through conventional circuitry.

As shown through the figures, an engagement means 51 of the clamp variety is designed to grasp the fuel rod 18 and hold it in position relative ,to the path of the functioning electrode 28 in the welding head. The clamping surfaces 52, and 53 of the engagement means 51 are provided with an aperture 54 which is in axial alignment with the path of the fuel rod 18 as it passes through the entrance port and is adapted to receive the fuel rod 18 upon its insertable travel through the chamber 10. The clamp 51 is of a vise type nature and is actuated by a conventional air-cylinder 55 of the pushpull variety through a linkage 56 upon being energized by the aforesaid power source.

In operation, the open end of an empty fuel rod 18 of the long, slender variety is inserted in the entrance port 14 and passed through the linear aperture 54 of the engagement 51 into the longitudinal passageway 24 of the shaft 23 and out through the exit port 15 of the chamber 10. At this point, a series of processing stations (not shown) are passed by the fuel rod wherein the fuel rod is loaded with radioactive material under an inert gaseous environment and adapted with a closure 61 on its open end. It should be noted that at some point before or during this initial stage, the enclosure is evacuated by the pump 12 and the desired gaseous environment is applied under a predetermined pressure from a gaseous source station 13 into such enclosure 10 until the desired state of conditions is obtained.

The loaded fuel rod 18 is then withdrawn through the exit port until it clears the passageway 24 and is spacially in position adjacent the inner surface of the engagement means 51. At which time, the air cylinder 44 is energized from a power source (not shown) and the retractable arm 41 is pivoted through a linkage 45 and shaft 42 into a position across the axial path of the fuel rod 18. The end of the latter rod, which is provided with the end closure 61 is then pushed into separable engagement with the arm 41 which functions as a stop controlling the further forward linear motion of the rod and positioning the juncture between the end-closure 61 and the fuel rod 18 operatively in the path of the rotating welding head 28. Subsequently, the air-cylinder 55 is energized through the power source and the fuel rod 18 is clamped in position by the closing action of the engagement means 51. The air-cylinder 44 then functions to retract the linkage 45 and pivot the arm 41 out of engagement with the end of the fuel rod 18 through the action of the shaft 42.

Rotary motion is then imparted to the plate 25 by a motive force 34 through the action of a gear train 32 and 33 thereby imparting rotary motion to the welding assembly 27 and electrode 28 in operative fashion around the periphery of the aforesaid external junction between the end-closure 61 and fuel rod 18. The sealing action of the weld head 27 is accomplished when energy is provided by the central power source (not shown) through the use of electrical contact finger assembly 31. As a result, the energized weld point or electrode 28 will seal the aforesaid juncture.

At the end of the welding cycle, the air-cylinder 39 will be activated and the cam 36 will move forward and through the cooperative action of arm 37, the welding head 27 will be moved out of its peripheral circuit or path thereby separating from engagement with the described juncture of the end closure 61 and fuel rod 18.

The clamping action of the engagement means 51 on the body of the fuel rod 18 is then relaxed by the retractive action of the air-cylinder 55 through the action of the linkage 56. As a result of this sealing process, the end-closure 61 is securely welded in position to the body of the fuel rod and may now be removed from the enclosure or chamber ready for use in the core of a nuclear reactor.

We claim:

1. A device for sealing an open-end nuclear reactor fuel rod comprising an enclosure having a pair of aligned openings, sealing means associated with said openings for engaging the fuel rod when the rod is received within said enclosure and for maintaining a vacuum and a gas under pressure within the enclosure, means for controlling the environment within said enclosure, a rotatably mounted shaft within said enclosure having a longitudinally disposed passageway in alignment with said pair of enclosure openings, a plate secured to one end of said shaft for rotation therewith, said plate having an opening in further alignment with said passageway and said enclosure openings, welding means secured to said plate for rotation with said plate,

drive means for rotating said plate and said welding means in a generally circular path about the fuel rod, an end closure for plugging the fuel rod open end, and an arm pivotally mounted within said enclosure to temporarily restrict the movement of the fuel rod through said passageway and engage said end closure on the fuel rod and to align the fuel rod and said end closure with said rotatable welding means.

2. A method for sealing an open-ended nuclear reactor fuel rod comprising the steps of inserting the open end of the rod entirely through an enclosure, loading the rod with nuclear fuel, evacuating the atmosphere within the enclosure, establishing a predetermined gaseous environment within said evacuated enclosure, placing a fuel rod end closure on the open end of the fuel rod, drawing the loaded fuel rod back into the enclosure, pivoting a pivotable arm into engagement with the loaded fuel rod to align the end closure with a welding assembly, clamping the loaded fuel rod in said aligned position, driving said welding assembly in a generally circular path about the end closure and the loaded fuel rod to weld the closure to the rod, and releasing the clamped fuel rod. 

1. A device for sealing an open-end nuclear reactor fuel rod comprising an enclosure having a pair of aligned openings, sealing means associated with said openings for engaging the fuel rod when the rod is received within said enclosure and for maintaining a vacuum and a gas under pressure within the enclosure, means for controlling the environment within said enclosure, a rotatably mounted shaft within said enclosure having a longitudinally disposed passageway in alignment with said pair of enclosure openings, a plate secured to one end of said shaft for rotation therewith, said plate having an opening in further alignment with said passageway and said enclosure openings, welding means secured to said plate for rotation with said plate, drive means for rotating said plate and said welding means in a generally circular path about the fuel rod, an end closure for plugging the fuel rod open end, and an arm pivotally mounted within said enclosure to temporarily restrict the movement of the fuel rod through said passageway and engage said end closure on the fuel rod and to align the fuel rod and said end closure with said rotatable welding means.
 2. A method for sealing an open-ended nuclear reactor fuel rod comprising the steps of inserting the open end of the rod entirely through an enclosure, loading the rod with nuclear fuel, evacuating the atmosphere within the enclosure, establishing a predetermined gaseous environment within said evacuated enclosure, placing a fuel rod end closure on the open end of the fuel rod, drawing the loaded fuel rod back into the enclosure, pivoting a pivotable arm into engagement with the loaded fuel rod to align the end closure with a welding assembly, clamping the loaded fuel rod in said aligned position, driving said welding assembly in a generally circular path about the end closure and the loaded fuel rod to weld the closure to the rod, and releasing the clamped fuel rod. 